Material, particularly for an optical component for use in microlithography, and method for making a blank from the material

• US 20070248522A1
• Filed: 04/18/2007
• Published: 10/25/2007
• Est. Priority Date: 04/20/2006
• Status: Active Grant

• Current Assignee: Heraeus Quarzglas GmbH & Co. KG (Heraeus Holding GMBH)
• Original Assignee: Heraeus Quarzglas GmbH & Co. KG (Heraeus Holding GMBH)
• Inventors: Kuehn, Bodo, Ochs, Stefan
• Granted Patent: US 7,691,766 B2
• Time in Patent Office: Days
• US Class Current: 423/324
• CPC Class Codes: C03C 10/0009 containing silica as main constituent
• CPC Class Codes: C04B 2235/6565 Cooling rate
• CPC Class Codes: C04B 2235/77 Density
• CPC Class Codes: C04B 2235/785 Submicron sized grains, i.e. from 0,1 to 1 micron
• CPC Class Codes: C04B 2235/786 Micrometer sized grains, i.e. from 1 to 100 micron
• CPC Class Codes: C04B 2235/94 Products characterised by their shape
• CPC Class Codes: C04B 2235/95 Products characterised by their size, e.g. microceramics
• CPC Class Codes: C04B 2235/9661 Colour
• CPC Class Codes: C04B 35/14 based on silica
• CPC Class Codes: C04B 35/645 Pressure sintering

Abstract

The invention is concerned with a material which shows low absorption for UV radiation having a wavelength below 250 nm, low birefringence, high chemical resistance and high radiation resistance and which is therefore particularly usable for Making optical components for microlithography. According to the invention the material consists of synthetically produced quartz crystallites which form a polycrystalline structure and have a mean grain size in the range between 500 nm and 30 μm. The method according to the invention for making a blank from the material comprises providing granules consisting of synthetically produced quartz crystals having a mean grain size in the range between 500 nm and 30 μm, and sintering the granules to obtain a blank of polycrystalline quartz.

Claims

1. A material for an optical component, said material comprising:

synthetically produced quartz crystallites that form a polycrystalline structure and that have a mean grain size in a range between 500 nm and 30 μ

m.

2. The material according to claim 1, wherein the quartz crystallites have a mean grain size in a range between 750 nm and 20 μ

m.

3. The material according to claim 1, wherein said material has a total porosity of less than 1 ppm.

4. The material according to claim 1, wherein the the quartz crystallites have pores with a size less than 1 μ

m.

15. The material of claim 1, wherein the material is used for an optical component in microlithography.

16. The material according to claim 1, wherein the quartz crystallites have a mean grain size in a range between 1 μ

m and 15 μ

m.

17. The material according to claim 1, wherein the quartz crystallites have a mean grain size in a range between 2 μ

m and 10 μ

m.

18. The material according to claim 1, wherein the quartz crystallites have pores with a size less than 0.5 μ

m.

5. A method for making a material, for an optical component said method comprising:

providing granules of synthetically produced quartz crystals having a mean grain size in a range between 500 nm and 30 μ

m, and

sintering the granules to obtain a blank of polycrystalline quartz.

6. The method according to claim 5, wherein the step of providing the granules comprises:

forming amorphous SiO₂ by hydrolysis or oxidation of a silicon compound which is vaporizable in a temperature range of up to 500°

C.,

using the amorphous SiO₂ as a raw material for preparing synthetic quartz seed crystal, and

processing the quartz seed crystal so as to form quartz crystal granules.

7. The method according to claim 6, wherein forming amorphous SiO₂ comprises depositing SiO₂ particles so as to form a massive preform of amorphous SiO₂.

8. The method according to claim 7, wherein the step of using the amorphous SiO₂ as the raw material for preparing the synthetic quartz seed crystal comprises breaking open the preform of amorphous SiO₂.

9. The method according to claim 7, wherein the preform is formed from porous SiO₂.

10. The method according to claim 7, wherein the step of preparing the synthetic quartz seed crystals is carried out by a hydrothermal method.

11. The method according to claim 6, wherein processing the quartz seed crystals so as to form quartz crystal granules comprises crushing the quartz seed crystals.

12. The method according to claim 5, wherein the synthetically produced quartz crystals have a mean grain size in a range between 750 nm and 20 μ

m.

13. The method according to claim 5, wherein the sintering of the quartz crystal granules to obtain a blank comprises gas pressure sintering.

14. The method according to claim 5, wherein a treatment is applied the blank to obtain a blank for an optical component, the treatment comprising removal of edge portions of the blank.

19. The method according to claim 5, wherein the synthetically produced quartz crystals have a mean grain size in a range between 1 μ

m and 15 μ

m.

20. The method according to claim 5, wherein the synthetically produced quartz crystals have a mean grain size in a range between 2 μ

m and 10 μ

m.